I think giving the white, yellow, orange, and green belts a better chance of winning by adding a higher resistance of getting dismembered or fractured. What I mean by this is that the lower belts will have to be hit harder and receive more damage than the higher belts so they have a more fighting chance.
In Layman's terms: give a custom (higher) DM and fracture threshold to the lower belts.

Pro: Lower belts will not feel so intimidated by getting smashed by a higher belt, and so come back to the game and play more.
Con: Misuse by some alternate accounts of higher belts.

Thanks.